Vehicle trailers of a minimum weight are usually equipped with braking systems independent of the towing vehicle. Non-commercial trailers used for horses, boats, RV's and campers usually incorporate electronic braking systems which are designed to be controlled by the towing vehicle. The braking systems are typically electronic in nature as opposed to pneumatic like semi-tractor brakes. The trailer brakes are important for larger loads because they ensure that the trailer stays in place and does not pass the towing vehicle during severe braking These braking systems are usually standardized and designed to accept control signals from an electronic brake controller mounted in within the towing vehicle. Two types of brake controllers typically exist. Those which are considered proportional and those that are not. Proportional electronic brake controllers are often considered safer and cause the trailer brakes to be applied at an intensity which is in proportion to the deceleration of the towing vehicle. As the deceleration of the towing vehicle increases the braking of the electronic trailer brakes also increases. The signal sent to the trailer brakes is able to be analog (0V to 12V for example) or pulse-width-modulated in nature.
One problem with the existing proportional trailer brake controllers is in the way that the controllers determine deceleration. Deceleration is measured using a pendulum or an electronic accelerometer. Consequently, the controllers must be installed properly on level ground and then adjusted to account for non-level mounting surfaces before they are able to operate effectively. In addition, the controllers often require tuning or a changing of the mounting angle before pulling a trailer. In both cases, acceleration due to the force of gravity is not filtered out and contributes to errors whenever the towing vehicle and trailer are traveling on a sloped roadway.